It is well known to vibrate the needle bar gate of a sewing machine to effect zigzag stitching by means of a zigzag cam which is driven by a worm gear meshing with a continuously rotating worm. In such an arrangement a cam follower is connected, through rather complicated mechanism, to the needle bar gate and, in order to obtain the necessary stability of the needle bar and needle particularly during work penetration and at needle thread loop seizure by the looptaker, it is essential that the various elements included in the mechanism connecting the cam follower to the needle bar gate be made to close tolerances. Moreover, operation of the sewing machine causes wear on the parts of the needle vibrating mechanism and in due time this wear affects the quality of zigzag stitching.